Not enough contrast with LCD!

Other Hardware Displays
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Using LCD: Winstar WH2004L-TMI-JT 20x4 Large Char LCD Display Blue Negative Mode
Using Adafruit Backpack
Using Adafruit LiquidCrystal Library, the I2C fork.

Text is being pushed onto the LCD, only barely visible when I turn the LCD contrast all the way down (text is dark) through the potentiometer on the Adafruit Backpack.

5V supply through the 5V pin, GND through Analog pin, SCL and SDA connected as normal.

5V falls to around 3.2V when backlight turns on. Text is visible (barely, this time due to lack of light (not a transreflective panel)) when backlight is off. Recently, jumbled text being displayed after a while, I think this is a wiring issue though, as it's only started after I have soldered in a weird way to the back of the PCB where the Arduino is mounted. The other issue remains even with proper connections.

If it is current limiting, why? The current draw on the datasheet is 1.2 mA, something the Arduino can easily provide. The board is rated for 5V use, and that's what I have been supplying. Any ideas?

Thanks!

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Why is the GND connected to an analog pin?
Connect GND to GND.

2 Likes
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Ok, I can try that. However, I am pulling the pin down, and it is in line with GND. If this isn't the issue, what else could be going wrong?

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Post a schematic diagram (hand drawn is fine), so people can see what you are actually trying to do.

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Check the current the backlight is using. It should be around 80mA according to this: https://static.rapidonline.com/pdf/57-2258.pdf and there is a diagram which shows an external current limiting resistor.

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For the external current limiting resistor, is there an indication of how large it should be? I will try a few values and see if that helps @6v6gt

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